Over the first two matches, Watson has managed just 72 runs at an average of 18.00, while Haddin has accumulated a meagre 21 at 7.00, sparking speculation the two 30-somethings could have been dropped for the Boxing Day Test at the MCG.
After Sunday's announcement of Australia's 13-man squad for the Melbourne fixture, it appears both Haddin and Watson will play and off-spinner Lyon is confident they will produce something with the bat before too long.
"Shane is a world-class batter and I can guarantee that he's being positive in his thinking," Lyon said in Melbourne in the lead-up to Friday's opening day of the third Test.
"I'm pretty sure he can come out and score some runs, as can Brad Haddin, who everyone thinks is under pressure as well.
"Brad's his normal self. He's a great leader... I'm sure he'll be able to get some runs when we need him too.
"He hasn't had the best run of luck in this Test match series but if you look back at the last series (the Ashes) here in Australia, he saved us in every Test match."
Haddin's last half-century at Test level came in the fifth match against England in Sydney in January, while he has not reached three figures since the Adelaide Test in the same series.
Watson's record is similar - a half-century at the MCG against England in 2013 and a century in Perth the previous Test.